1. Field of the Invention
This invention relates to an improved in a motor vehicle to reduce the noise level thereof, and more particularly to a noise emission preventing device for use in an automotive vehicle, by which the engine noise is effectively prevented from being emitted outside the vehicle.
2. Description of the Prior Art
In a technique of preventing engine noise emission from a motor vehicle, there has been conventionally used an enclosure type engine noise insulating device wherein the engine is enclosed substantially in a sealed condition by means of a noise insulating plate. Such a conventional insulating device, though it has a considerable insulating effect, is defective in that the structure is too complicated, requires a large number of parts and is inferior with regard to ease and frequency of maintenance. There is also a problem with regard to the internal thermal load with respect to the cooling of the engine, which requires a separate means for reducing the thermal load. Further, as the noise insulating plate is supported by the engine body, the vibration (particularly the low frequency component) of the engine body is transmitted to the noise insulating plate, even though an elastic support manner is employed. The noise insulating plate will therefore become a second noise source and consequently weaken the noise insulating effect. Accordingly, such a conventional device does not meet desired requirements and thus is difficult to be put to practical use.